1. Field of the Invention
The present invention relates to a switching regulator, and more particularly to a switching regulator that can achieve both responsiveness and stability at the time of light load and at the time of heavy load.
2. Description of the Related Art
Switching regulators are used in various types of electronic devices. In the switching regulator, as compared with a linear regulator, power conversion efficiency can be enhanced whereas its noise resistance characteristic is often problematic. In the switching regulator, responsiveness and stability at the time of heavy load and at the time of light load are also often problematic.
Japanese Unexamined Patent Application Publication No. 2013-143831 discloses a switching regulator of a PWM control system, and a method of controlling it. This switching regulator includes a PWM comparator that compares the output voltage of an error amplifier with a slope voltage, and a first offset circuit and a second offset circuit that are formed with a constant current circuit are connected to the side of an input terminal to which the slope voltage is applied. In the configuration described above, at the time of heavy load, the first offset circuit is operated, and at the time of light load, both the offset circuits are operated, with the result that the operation point of the PWM comparator is adjusted.
Japanese Unexamined Patent Application Publication No. 2008-206239 provides a switching regulator in which when a load is rapidly reduced, even in a current mode system, an output voltage is not brought into an oscillation state, and thus the overshoot of the output voltage is reduced. In order to achieve its object, a circuit configuration is proposed in which an offset voltage is applied to the side of a terminal to which a so-called target voltage of an error amplifier is applied.
Japanese Unexamined Patent Application Publication No. 2012-55129 provides a switching regulator that reduces variations in output voltage. In order to achieve its object, a correction portion is provided that lowers a voltage input to an error amplifier to a predetermined value or less.
Domestic Re-publication of PCT International Publication No. 2005/078910 provides a switching power supply device that reduces loss at the time of light load to improve efficiency. It discloses a voltage source that applies an offset voltage to a current detection voltage obtained by detecting and converting a current value flowing through a coil into a voltage value.